In PCT application WO 88/02087, published Mar. 10, 1988 by Michael Laumen, a steam generator is disclosed having a porous sintered metal block in a housing as a steam generation element. The sintered block is electrically heated to a predetermined temperature so that steam is formed and then directed out of the housing.
FIG. 1 is a simplified Laumen steam generator of the type described in publication WO 88/02087. The apparatus uses a sintered metal block 12 in a conical housing 14 as a steam generating element. The sintered metal block 12 has metal grain size and porosity optimized for steam generation. The block divides the conical housing, receiving pressurized water from a water feed 18 to form a water layer 22 below the block. Pressure forces water from the layer 22 into pores of the sintered metal block, with the metal selected for good heat conductivity.
An electrical heater 16 is a coil that heats the block by conduction through the housing wall and into the block thereby causing evaporation of the water in the pores of the block upwardly into the steam chamber 32. A temperature probe 26 measures the temperature of evaporating water and applies electricity from electrical power source 42 to the coils as needed to form steam. A water supply 34 sends water to a filter 36 for purification and then to pressurizing pump 38 to supply the water feed 18 to form the water layer 22 below the metal block, with the upper portion of the water layer 22 entering the block. A heat exchanger 20 cools the outside of the housing 14 to recover outward conduction of heat from the coil. Meanwhile, continuing layers of water, converted to steam, form a cloud of steam in steam chamber 32, then exit the housing through the steam vent tube 40. The vent tube has a feedback loop, not shown, to the pump 38 so that steam output may be regulated to a desired amount and another feedback loop 46 regulating power to coil 16 for regulating heat.
While the Laumen steam generator is very good for producing desired amounts of steam, a problem is that the quality of the steam is not suitable for some applications, particularly for scientific or medical laboratory applications where very pure steam is desired. This problem arises because in the metal sintering process, fine particles of carbon or metal or metal compounds are formed that can occupy the interstices of the granular metal block. Some of these fine particles are picked up by the steam in the evaporation process. What is needed is a steam forming method that produces ultrapure steam for scientific or medical laboratory applications.